INORGANIC MANURE. 193 



A most remarkable and important result follows from this ex- 

 periment — that when potatoes, wheat, turnips, peas, and clover 

 (fotash, lime, and silica plants), are cultivated successively on 

 the same field, although this field had been thrice manured in the 

 course of sixteen years, the same relation of nitrogen to a given 

 quantity of carbon is obtained, as m the case of a meadow which 

 had received no manure. 



Carbon. Nitrogen. 

 Upon an acre of meadow land there is cropped of silica, ) q-. r>n-Q 



lime, and potash plants, taken together - - $ 

 On an acre of arable land, on a sixteen years' average, of ) .„ _ fi . s 



silica, lime, and potash plants - - - j "' 



When we take into consideration the amount of carbon and 

 nitrogen in the leaves of the beet and potatoe (for the leaves 

 were not calculated in the produce of the arable land), then it 

 follows that, notwithstanding all the supply of carbon and of ni- 

 trogen furnished in the manure, the arable land has not produced 

 more of these elements than an equal surface of meadow land, 

 which received only mineral food (constituents of the soil). 



Then, on what depends the peculiar action of manures, 

 and of the liquid and solid excrements of animals 7 



This question is susceptible of a simple solution. These 

 manures have a very decided action on our arable land, from 

 which for centuries we have removed, in the form of cattle and 

 of corn, a certain quantity of constituents of the soil which have 

 not been restored. 



If no manure had been applied to the land during the sixteen 

 years of the above experiment, the crop would have mounted to 

 only a half or third part of the carboa and nitrogen. 



The liquid and solid excrements used as manure enabled this 

 surface of arable land to produce as much as the meadow land. 



But notwithstanding the amount of manure supplied, the field 

 was no richer in the mineral food of plants on the sixth year, 

 when it was manured anew, than it was the first year. In the 

 second year after manuring, it contained less mineral food than 

 on the first year ; and after the fifth year it became so much ex- 

 hausted that it was necessary, in order to obtain crops as rich as 

 the first year, to give buck to the field all the mineral constituents 

 10 . • - ;' 



